U.S. Pat. No. 5,980,785 to Xi, et al. broadly teaches compositions useful in electronic applications created by screen-printing pastes, followed by heat and/or chemical reaction induced solidification. However as the electronics industry advances, many such pastes must be increasingly resistant to water sorption in high humidity, high temperature environments.
Furthermore, when a resistor film is screen printed and solidified upon a conductive substrate, a reliable and stable bond must be formed at the interface (between the conductive substrate and the resistor film). If not, resistor properties can tend to drift or otherwise become problematic. If a traditional PTF resistor film is bonded directly to a copper trace, the resistance properties will generally drift, due to instability and unreliability at the resistor/conductor interface. Consequently, before conventional resistor films are applied to a copper trace, the copper trace is typically plated with silver (e.g., the copper trace is first exposed to a silver immersion plating process), since silver at the interface (between the resistor film and the copper trace) will generally provide a more stable and reliable interface, resulting in improved resistor performance. However, silver plating can be expensive and can add to the overall complexity of the manufacturing process. A need therefore also exists for resistor film compositions capable of being applied directly to copper traces with improved interface reliability and stability, relative to known resistor film compositions.